Assessment of endogenous and exogenous silver nanoparticles effects on the microalgae Chlorella vulgaris.

Microalgae are susceptible to most pollutants in aquatic ecosystems and can be potentially damaged by silver nanoparticles (AgNPs). This study aims to clarify the potential consequences of Chlorella vulgaris internalizing AgNPs. The exposure of C. vulgaris to AgNPs stabilized with citrate led to the accumulation of NPs in the cell wall, increasing permeability, which allowed the entry of AgNPs and Ag + ions resulting from the dissolution of AgNPs. Ag + accumulated inside the cell could be converted into AgNPs (endogenous) due to the reducing potential of the cytoplasm. Both exogenous and endogenous AgNPs caused damage to all biological structures of the algae, as demonstrated by TEM images. This damage included the disorganization of chloroplasts, deposition of AgNPs on starch granules, and increased amounts of lipids, starch granules, exopolysaccharides, plastoglobuli, and cell diameters. These changes caused cell death by altering cell viability and interfering with organelle functions, possibly due to reactive oxygen species generated by nanoparticles, as shown in a lipid bilayer model. These findings highlight the importance of considering the exposure risks of AgNPs in a worldwide distributed chlorophyte.

Microalgae separation in MP-PVC contaminated wastewater using plant-based coagulant over different extraction methods in Bauru, Brazil.

This study investigates the effectiveness of coagulation-flocculation and sedimentation (CFS) for separating microalgae, focusing on the use of various Moringa oleifera extracts as natural coagulants. We examined photobioreactor effluent (PBR) both with and without microplastic PVC (MP-PVC) contamination, referred to as PBR R2 and PBR R1, respectively. Utilising response surface methodology, we identified optimal conditions for the removal of microalgae and MP-PVC. Validation tests demonstrated that the aqueous extract of delipidated Moringa oleifera powder (AEDMOP) achieved high removal efficiencies, with coagulant dosages of 630 mg L-1 for PBR R1 and 625 mg L-1 for PBR R2. Both conditions showed microalgae removal efficiencies exceeding 83% for turbidity, colour, OD540 nm, OD680 nm, and OD750 nm, and 63% for OD254 nm. Interestingly, the optimised conditions for PBR R2 required slightly less coagulant, likely due to the additional particulate matter from MP-PVC. While extracellular polymeric substances (EPS) exhibited a marginal effect on flocculation, further investigation into their role in CFS is necessary. Our findings highlight the potential of AEDMOP for efficient microalgae separation, even in the presence of microplastics.

Pollution control and biodiesel production with microalgae: new perspectives on the use of flat panel photobioreactors regarding variation in volume application rate.

In the present study, the microalga Arthrospira platensis DHR 20 was cultivated in vertical flat-plate photobioreactors (FPBRs) to bioremediate anaerobically digested cattle wastewater (ACWW) and used as a growth substrate. The final objective was to evaluate the properties of the oil extracted from this biomass to determine its potential for biodiesel production. The process was divided into five phases, varying the volume of the applied substrate: 1 L (Phase I), 5 L (Phase II), 10 L (Phase III), 15 L (Phase IV), and 20 L (Phase V). Dry biomass reached a maximum of 5.7 g L-1, and productivity peaked at 0.74 g L-1d-1. The highest rate of CO2 biofixation was 1213.5 mg L-1 day-1, showing good potential for purifying the air. The highest specific maximum growth rate (µmax) and the shortest doubling time (Dt) were found during Phase I. The removal of pollutants and nutrients during the experimental phases ranged from 65.8% to 87.1% for chemical oxygen demand (COD), 82.2% to 85.8% for total organic carbon (TOC), 91% to 99% for phosphate (PO43-), 62.5% to 93% for nitrate (NO3-), 90.4% to 99.7% for ammoniacal nitrogen (NH4+), and 86.5% to 98.5% for total nitrogen (TN). The highest lipid production recorded was 0.172 g L-1 day-1. The average cetane number recorded in Phase IV of 51 suggests that the fuel will ignite efficiently and consistently, providing smooth operation and potentially reducing pollutant emissions. The analysis of fatty acids revealed that the produced biodiesel has the potential to be used as an additive for other low-explosive biocombustibles, representing an innovative and sustainable approach that simultaneously offers bioremediation and carbon sequestration.

Toxicity potential of a pyraclostrobin-based fungicide in plant and green microalgae models.

Pyraclostrobin-based fungicides play an effective role in controlling fungal diseases and are extensively used in agriculture. However, there is concern regarding the potential adverse effects attributed to exposure to these fungicides on non-target organisms and consequent influence exerted on ecosystem functioning. Thus, it is essential to conduct studies with model organisms to determine the impacts of these fungicides on different groups of living organisms. The aim of this study was to examine the ecotoxicity associated with exposure to commercial fungicides containing pyraclostrobin. The focus of the analysis involved germination and initial development of seedlings of 4 plant models (Lactuca sativa, Raphanus sativus, Pennisetum glaucum and Triticum aestivum), in addition to determining the population growth rate and total carbohydrate content in microalga Raphidocelis subcapitata. The fungicide pyraclostrobin adversely influenced growth and development of the tested plants, indicating a toxic effect. The fungicide exerted a significant impact on the initial development of seedlings of all model species examined with T. aestivum plants displaying the greatest susceptibility to pyraclostrobin. Plants of this species exhibited inhibitory effects on both aerial parts and roots when treated with a concentration of 4.75 mg/L pyraclostrobin. In addition, the green microalga R. subcapitata was also significantly affected by the fungicide, especially at relatively high concentrations as evidenced by a reduction in total carbohydrate content. This commercial fungicide demonstrated potential phytotoxicity for the tested plant models and was also considered toxic to the selected microalgae, indicating an ecotoxic effect that might affect other organisms in aquatic environments.

Development and evaluation of low-cost flat plate photobioreactors for microalgae and cyanobacteria cultivation with biotechnological potential.

The high performance of biomass and metabolite biosynthesis by photosynthetic microorganisms is directly influenced by the cultivation system employed. Photobioreactors (PBRs) stand out as controlled and fundamental systems for increasing the production of biocompounds. However, the high costs associated with these systems hinder their viability. Thus, a more practical and economical approach is necessary. Accordingly, this study aimed to design and evaluate low-cost flat-panel photobioreactors on a laboratory scale for the cultivation of photosynthetic microorganisms, using economical materials and instruments. Additionally, internal optimization of the low-cost system was aimed to maximize growth and biomass production. The PBRs were designed and built with uniform dimensions, employing 4 mm translucent glass and agitation through compressors. The internally optimized system (PBR-OII) was equipped with perforated acrylic plates used as static mixers. To evaluate the performance of the low-cost PBR-OII, a comparison was made with the control photobioreactor (PBR-CI), of the same geometry but without internal optimization, using a culture of Synechocystis sp. CACIAM 05 culture. The results showed that the PBR-OII achieved maximum biomass yield and productivity of 6.82 mg/mL and 250 mg/L/day, respectively, values superior to the PBR-CI (1.87 mg/mL and 62 mg/L/day). Additionally, the chlorophyll concentration in the PBR-OII system was 28.89 ± 3.44 µg/mL, while in the control system, the maximum reached was 23.12 ± 1.85 µg/mL. Therefore, low-cost photobioreactors have demonstrated to be an essential tool for significantly increasing biomass production, supporting research, and reducing costs associated with the process, enabling their implementation on a laboratory scale.

Effect of calcium-enriched microalgae extract on mitigating saline stress in papaya seedlings.

The papaya (Carica papaya L.) is among the mainly fruit species produced in tropical and subtropical climate. The salinity of water in agricultural areas is considered a limiting factor for the expansion of papaya. This study aimed to evaluate calcium-enriched microalgae extract (EMa-Ca) as an attenuator of saline stress in irrigation water on the growth and physiology of Formosa papaya seedlings, hybrid Tainung. The experiment was conducted in a protected environment, with treatments distributed in a 5 × 2 factorial scheme, comprising five electrical conductivities of irrigation water (0.50; 1.10; 2.50; 3.90 and 4.50 dSm-1) with the presence and absence of EMa-Ca in the substrate. Evaluated characteristics were: plant height, number of leaves, stem diameter, leaf area, dry masses weight of roots, aboveground parts and total. Gas exchanges and chlorophyll indices (a, b and total) were also evaluated. The application of EMa-Ca resulted in an increase of 6.05% in height and 6.33% in trunk diameter. The number of leaves decreased with an increase in electrical conductivity, and the leaf area was reduced by 33%. All seedling dry masses showed greater declines in the absence of EM-Ca. The EMa-Ca increased net photosynthesis, CO2 concentration, transpiration and stomatal conductance by 39.13%, 30.43%, 38.88% and 42.85%, respectively. For chlorophyll without the use of EMa-Ca, a decrease rate of 1.21%, 0.41% and 1.62% was observed for Chla, Chlb and Chlt, respectively. Therefore, the EMa-Ca application (1.0 ml/L) significantly enhance the vegetative development, gas exchanges, and chlorophyll indices of papaya seedlings under saline stress conditions.

Increase in polyunsaturated fatty acids and carotenoid accumulation in the microalga Golenkinia brevispicula (Chlorophyceae) by manipulating spectral irradiance and salinity.

Microalgal biotechnology offers a promising platform for the sustainable production of diverse renewable bioactive compounds. The key distinction from other microbial bioprocesses lies in the critical role that light plays in cultures, as it serves as a source of environmental information to control metabolic processes. Therefore, we can use these criteria to design a bioprocess that aims to stimulate the accumulation of target molecules by controlling light exposure. We study the effect on biochemical and photobiological responses of Golenkinia brevispicula FAUBA-3 to the exposition of different spectral irradiances (specifically, high-fluence PAR of narrow yellow spectrum complemented with low intensity of monochromatic radiations of red, blue, and UV-A) under prestress and salinity stress conditions. High light (HL) intensity coupled to salinity stress affected the photosynthetic activity and photoprotection mechanisms as shown by maximal quantum yield (Fv/Fm) and non-photochemical quenching (NPQmax) reduction, respectively. HL treatments combined with the proper dose of UV-A radiation under salinity stress induced the highest carotenoid content (2.75 mg g dry weight [DW]- 1) composed mainly of lutein and ß-carotene, and the highest lipid accumulation (35.3% DW) with the highest polyunsaturated fatty acid content (alpha-linolenic acid (C18:3) and linoleic acid (C18:2)). Our study can guide the strategies for commercial indoor production of G. brevispicula for high-value metabolites.

Antiviral Effect of Microalgae Phaeodactylum tricornutum Protein Hydrolysates against Dengue Virus Serotype 2.

Dengue, caused by the dengue virus (DENV), is a global health threat transmitted by Aedes mosquitoes, resulting in 400 million cases annually. The disease ranges from mild to severe, with potential progression to hemorrhagic dengue. Current research is focused on natural antivirals due to challenges in vector control. This study evaluates the antiviral potential of peptides derived from the microalgae Phaeodactylum tricornutum, known for its bioactive compounds. Microalgae were cultivated under controlled conditions, followed by protein extraction and hydrolysis to produce four peptide fractions. These fractions were assessed for cytotoxicity via the MTT assay and antiviral activity against DENV serotype 2 using flow cytometry and plaque formation assays. The 10-30 kDa peptide fraction, at 150 and 300 µg/mL concentrations, demonstrated no cytotoxicity and significantly reduced the percentage of infected cells and viral titers. These findings suggest that peptides derived from Phaeodactylum tricornutum exhibit promising antiviral activity against dengue virus serotype 2, potentially contributing to developing new therapeutic approaches for dengue.

Unlocking pilot-scale green diesel production from microalgae.

Microalgae have emerged as a promising source of biomass to produce renewable biofuels due to their ability to synthesize high-energy density compounds of commercial interest. This study proposes an approach for pilot-scale oil extraction, purification by fractional distillation, hydrocarbon characterization by gas chromatography coupled to mass spectrometry (GC-MS), evaluation of physicochemical parameters of the produced hydrocarbons, preliminary cost analysis, and challenges and future opportunities for green diesel on a commercial scale. Here, the microalgae Tetradesmus obliquus was cultivated in 12 m³ photobioreactors using biodigested swine waste as a culture medium. The resulting biomass was subjected to drying and harvesting, followed by oil extraction using a hot solvent extraction method, followed by distillation to purify the compounds. Three different extraction and distillation experiments were conducted, each using different solvent combinations. The results obtained revealed that extraction with a solvent blend, composed of hexane and ethanol, provided more significant yields compared to extraction with pure hexane. GC-MS analysis showed the presence of alkanes and alkenes in the oil samples, and the proportion of solvent used in the extraction directly influenced the production of alkanes. Additionally, specific hydrocarbons such as 4-methyl-1-decene, 8-heptadecene, 1-pentadecene, 9-heneicosene, and 2-dodecene were identified. The evaluation of the physicochemical parameters demonstrated that the calorific value of the distilled oil samples is within the range of typical values for petroleum diesel. However, it was observed that the distilled oil samples had higher sulfur content compared to conventional diesel. Regarding the cost analysis, it was found that it varies depending on the experimental conditions. In particular, the process using a solvent mixture of 70% hexane and 30% ethanol proved to be more economical than the others, since it extracted a greater quantity of oil with a lower initial biomass requirement. In summary, this microalgae-derived hydrocarbon production process is promising and offers insights for compound purification and future biofuel applications.

Use of Residual Lignocellulosic Biomass and Algal Biomass to Produce Biofuels.

Efforts are intensifying to identify new biofuel sources in response to the pressing need to mitigate environmental pollutants, such as greenhouse gases, which are key contributors to global warming and various worldwide calamities. Algae and microalgae present themselves as excellent alternatives for solid-gaseous fuel production, given their renewable nature and non-polluting characteristics. However, making biomass production from these organisms economically feasible remains a challenge. This article collates various studies on the use of lignocellulosic waste, transforming it from environmental waste to valuable organic supplements for algae and microalgae cultivation. The focus is on enhancing biomass production and the metabolites derived from these biomasses.

Traditional and new trend strategies to enhance pigment contents in microalgae.

Microalgae are a source of a wide variety of commodities, including particularly valuable pigments. The typical pigments present in microalgae are the chlorophylls, carotenoids, and phycobiliproteins. However, other types of pigments, of the family of water-soluble polyphenols, usually encountered in terrestrial plants, have been recently reported in microalgae. Among such microalgal polyphenols, many flavonoids have a yellowish hue, and are used as natural textile dyes. Besides being used as natural colorants, for example in the food or cosmetic industry, microalgal pigments also possess many bioactive properties, making them functional as nutraceutical or pharmaceutical agents. Each type of pigment, with its own chemical structure, fulfills particular biological functions. Considering both eukaryotes and prokaryotes, some species within the four most promising microalgae groups (Cyanobacteria, Rhodophyta, Chlorophyta and Heterokontophyta) are distinguished by their high contents of specific added-value pigments. To further enhance microalgae pigment contents during autotrophic cultivation, a review is made of the main related strategies adopted during the last decade, including light adjustments (quantity and quality, and the duration of the photoperiod cycle), and regard to mineral medium characteristics (salinity, nutrients concentrations, presence of inductive chemicals). In contrast to what is usually observed for growth-related pigments, accumulation of non-photosynthetic pigments (polyphenols and secondary carotenoids) requires particularly stressful conditions. Finally, pigment enrichment is also made possible with two new cutting-edge technologies, via the application of metallic nanoparticles or magnetic fields.

Hematological and anthelminthic responses of tambaqui (Colossoma macropomum) supplemented with Artrhospira platensis and Chlorella vulgaris.

The present study evaluated the hematological, antiparasitic and growth responses in tambaqui (Colossoma macropomum) fed with diets supplemented with the microalgae Arthrospira platensis and Chlorella vulgaris (0%; 10% A. platensis; 10% C. vulgaris; and 5% A. platensis+5% C. vulgaris). Tambaqui (n=60, 62.57 ± 8.76 g) were fed for 20 days with experimental diets. Blood samples collection was done to determine hematological parameters, and gills were removed to identify and count monogenetic parasites. Supplementation with A. platensis 10% reduced red blood cells count, in consequence mean corpuscular volume and mean hemoglobin concentration increased. Total leukocyte, monocyte, eosinophil, and basophil counts reduced with the use of A. platensis. Higher monocytes, eosinophil, and basophil numbers in tambaqui fed with diet supplemented with 10% C. vulgaris were observed and may have been due to the presence of immunostimulants in this microalga composition. Reduction on total cholesterol in tambaqui that received both microalgae (A. platensis 5%+C. vulgaris 5%) may indicate that combined supplementation presented greater benefits to the health for C. macropomum than separately. Both microalgae were efficient against monogenetic parasites of tambaqui. Thus, the dietary use of the microalgae A. platensis and C. vulgaris provided immunostimulant and antiparasitic efficacy in C. macropomum.

Efficient PAHs removal and CO2 fixation by marine microalgae in wastewater using an airlift photobioreactor for biofuel production.

Microalgae cultures have emerged as a promising strategy in diverse areas, ranging from wastewater treatment to biofuel production, thus contributing to the search for carbon neutrality. These photosynthetic organisms can utilize the resources present in wastewater and fix atmospheric CO2 to produce biomass with high energy potential. In this study, the removal efficiency of Polycyclic Aromatic Hydrocarbons (PAHs), CO2 fixation and lipid content in the biomass produced from microalgae grown in airlift photobioreactor were evaluated. Four mesoscale cultures were carried out: Control (Seawater + Conway medium), Treatment A (Oil Produced Water + Poultry Effluent Water), Treatment B (Poultry Effluent Water + Seawater) and Treatment C (Oil Produced Water, Seawater and nutrients). The impact of biostimulation, through the addition of nutrients, on PAHs removal efficiency (up to 90%), CO2 fixation rate (up to 0.20 g L-1 d-1) and the composition of the generated biomass was observed. Primarily, the addition of nitrates to the culture medium impacted CO2 fixation rate of the microalgae. In addition, a direct correlation was observed between PAHs removal and lipid accumulation in the biomass, up to 36% in dry weight, demonstrating microalgae's ability to take advantage of the organic carbon (PAHs) present in the culture medium to generate lipid-rich biomass. The concentration of polysaccharides in the biomass obtained did not exceed 12% on a dry weight basis, and the Higher Heating Value (HHV) ranged between 17 and 21 MJ kg-1. Finally, the potential of generating hydrogen through pyrolysis was highlighted, taking advantage of the characteristics of biomass as a conversion route to produce biofuels. These results show that microalgae are effective in wastewater treatment and have great potential in producing biofuels, thus contributing to the transition towards more sustainable energy sources and climate change mitigation.

Alternative green solvents associated with ultrasound-assisted extraction: A green chemistry approach for the extraction of carotenoids and chlorophylls from microalgae.

This study proposes a method for the ultrasonic extraction of carotenoids and chlorophyll from Scenedesmus obliquus and Arthrospira platensis microalgae with green solvents. Ethanol and ethanolic solutions of ionic liquids were tested with a variety of extraction parameters, including number of extractions, time of extraction, and solid-liquid ratio R(S/L), to determine the optimal conditions. After selecting the most effective green solvent (ethanol), the process conditions were established: R(S/L) of 1:10, three extraction cycles at 3 min each), giving an extraction yield of 2602.36 and 764.21 µgcarotenoids.gdried biomass-1; and 22.01 and 5.81 mgchlorophyll.gdried biomass-1 in S. obliquus and A. platensis, respectively. The carotenoid and chlorophyll extracts obtained using ethanol were shown to be potent scavengers of peroxyl radical, being 5.94 to 26.08 times more potent α-tocopherol. These findings pave the way for a green strategy for valorizing microalgal biocompounds through efficient and environmentally friendly technological processes.

Effects of Cadmium and Nickel Mixtures on Multiple Endpoints of the Microalga Raphidocelis subcapitata.

It is crucial to investigate the effects of mixtures of contaminants on aquatic organisms, because they reflect what occurs in the environment. Cadmium (Cd) and nickel (Ni) are metals that co-occur in aquatic ecosystems, and information is scarce on their joint toxicity to Chlorophyceae using multiple endpoints. We evaluated the effects of isolated and combined Cd and Ni metals on multiple endpoints of the chlorophycean Raphidocelis subcapitata. The results showed that Cd inhibited cell density, increased reactive oxygen species (ROS) production (up to 308% at 0.075 mg L-1 of Cd), chlorophyll a (Chl a) fluorescence (0.050-0.100 mg L-1 of Cd), cell size (0.025-0.100 mg L-1 of Cd), and cell complexity in all concentrations evaluated. Nickel exposure decreased ROS production by up to 25% at 0.25 mg L-1 of Ni and Chl a fluorescence in all concentrations assessed. Cell density and oxygen-evolving complex (initial fluorescence/variable fluorescence [F0/Fv]) were only affected at 0.5 mg L-1 of Ni. In terms of algal growth, mixture toxicity showed antagonism at low doses and synergism at high doses, with a dose level change greater than the median inhibitory concentration. The independent action model and dose-level-dependent deviation best fit our data. Cadmium and Ni mixtures resulted in a significant increase in cell size and cell complexity, as well as changes in ROS production and Chl a fluorescence, and they did not affect the photosynthetic parameters. Environ Toxicol Chem 2024;43:1855-1869. © 2024 SETAC.

A Comparison of Monoglyceride Production from Microalgaelipids and Rapeseed Oil Catalyzed by Metal Oxides.

This manuscript reports for the first time a heterogenous catalytic route to monoglycerides (MAGs) from microalgal oil. Microalgae is an important biomass source with high-value applications, such as food ingredients with essential fatty acids. To date, the glycerolysis of microalgae has only been investigated for a microbial oil (Schizochytrium sp.) using enzyme catalysis. However, the use of enzymes on a large scale is currently economically impeditive and requires highly selective lipases. In this study, metal oxides were screened and the reaction conditions optimized for rapeseed oil. The optimized conditions were then used to investigate the production of MAGs from Scenedesmus sp. microalga. The most promising catalyst was found to be MgO/KOH, which gave a 44 % yield. Comparing two reaction systems (low temperature 70 °C/atmospheric pressure and high temperature at 200 °C/20 bar), it was found that the latter has a superior performance. Due to the stability of the product in air, the presence of an inert atmosphere is essential to achieve high yields.

Microalgae-mediated biofixation as an innovative technology for flue gases towards carbon neutrality: A comprehensive review.

Microalgae-mediated industrial flue gas biofixation has been widely discussed as a clean alternative for greenhouse gas mitigation. Through photosynthetic processes, microalgae can fix carbon dioxide (CO2) and other compounds and can also be exploited to obtain high value-added products in a circular economy. One of the major limitations of this bioprocess is the high concentrations of CO2, sulfur oxides (SOx), and nitrogen oxides (NOx) in flue gases, according to the origin of the fuel, that can inhibit photosynthesis and reduce the process efficiency. To overcome these limitations, researchers have recently developed new technologies and enhanced process configurations, thereby increased productivity and CO2 removal rates. Overall, CO2 biofixation rates from flue gases by microalgae ranged from 72 mg L-1 d -1 to over 435 mg L-1 d-1, which were directly influenced by different factors, mainly the microalgae species and photobioreactor. Additionally, mixotrophic culture have shown potential in improving microalgae productivity. Progress in developing new reactor configurations, with pilot-scale implementations was observed, resulting in an increase in patents related to the subject and in the implementation of companies using combustion gases in microalgae culture. Advancements in microalgae-based green technologies for environmental impact mitigation have led to more efficient biotechnological processes and opened large-scale possibilities.

Integrating electro-Fenton and microalgae for the sustainable management of real food processing wastewater.

The present study demonstrates, for the first time, the feasibility of a two-step process consisting of Electro-Fenton (EF) followed by microalgae to treat highly loaded real food processing wastewater along with resource recovery. In the first step, EF with a carbon felt cathode and Ti/RuO2-IrO2 anode was applied at different current densities (3.16 mA cm-2, 4.74 mA cm-2 and 6.32 mA cm-2) to decrease the amount of organic matter and turbidity and enhance biodegradability. In the second step, the EF effluents were submitted to microalgal treatment for 15 days using a mixed culture dominated by Scenedesmus sp., Chlorosarcinopsis sp., and Coelastrum sp. Results showed that current density impacted the amount of COD removed by EF, achieving the highest COD removal of 77.5% at 6.32 mA cm-2 with >95% and 74.3% of TSS and PO43- removal, respectively. With respect to microalgae, the highest COD removal of 85% was obtained by the culture in the EF effluent treated at 6.32 mA cm-2. Remarkably, not only 85% of the remaining organic matter was removed by microalgae, but also the totality of inorganic N and P compounds, as well as 65% of the Fe catalyst that was left after EF. The removal of inorganic species also demonstrates the high complementarity of both processes, since EF does not have the capacity to remove such compounds, while microalgae do not grow in the raw wastewater. Furthermore, a maximum of 0.8 g L-1 of biomass was produced after cultivation, with an accumulation of 32.2% of carbohydrates and 25.9% of lipids. The implementation of the two processes represents a promising sustainable approach for the management of industrial effluents, incorporating EF in a water and nutrient recycling system to produce biomass that could be valorized into clean fuels.

De novo transcriptome and lipidome analysis of Desmodesmus abundans under model flue gas reveals adaptive changes after ten years of acclimation to high CO2.

Microalgae's ability to mitigate flue gas is an attractive technology that can valorize gas components through biomass conversion. However, tolerance and growth must be ideal; therefore, acclimation strategies are suggested. Here, we compared the transcriptome and lipidome of Desmodesmus abundans strains acclimated to high CO2 (HCA) and low CO2 (LCA) under continuous supply of model flue gas (MFG) and incomplete culture medium (BG11-N-S). Initial growth and nitrogen consumption from MFG were superior in strain HCA, reaching maximum productivity a day before strain LCA. However, similar productivities were attained at the end of the run, probably because maximum photobioreactor capacity was reached. RNA-seq analysis during exponential growth resulted in 16,435 up-regulated and 4,219 down-regulated contigs in strain HCA compared to LCA. Most differentially expressed genes (DEGs) were related to nucleotides, amino acids, C fixation, central carbon metabolism, and proton pumps. In all pathways, a higher number of up-regulated contigs with a greater magnitude of change were observed in strain HCA. Also, cellular component GO terms of chloroplast and photosystems, N transporters, and secondary metabolic pathways of interest, such as starch and triacylglycerols (TG), exhibited this pattern. RT-qPCR confirmed N transporters expression. Lipidome analysis showed increased glycerophospholipids in strain HCA, while LCA exhibited glycerolipids. Cell structure and biomass composition also revealed strains differences. HCA possessed a thicker cell wall and presented a higher content of pigments, while LCA accumulated starch and lipids, validating transcriptome and lipidome data. Overall, results showed significant differences between strains, where characteristic features of adaptation and tolerance to high CO2 might be related to the capacity to maintain a higher flux of internal C, regulate intracellular acidification, active N transporters, and synthesis of essential macromolecules for photosynthetic growth.

Metagenomic analysis of microbial consortia native to the Amazon, Highlands, and Galapagos regions of Ecuador with potential for wastewater remediation.

Native microbial consortia have been proposed for biological wastewater treatment, but their diversity and function remain poorly understood. This study investigated three native microalgae-bacteria consortia collected from the Amazon, Highlands, and Galapagos regions of Ecuador to assess their metagenomes and wastewater remediation potential. The consortia were evaluated for 12 days under light (LC) and continuous dark conditions (CDC) to measure their capacity for nutrient and organic matter removal from synthetic wastewater (SWW). Overall, all three consortia demonstrated higher nutrient removal efficiencies under LC than CDC, with the Amazon and Galapagos consortia outperforming the Highlands consortium in nutrient removal capabilities. Despite differences in α- and ß-diversity, microbial species diversity within and between consortia did not directly correlate with their nutrient removal capabilities. However, all three consortia were enriched with core taxonomic groups associated with wastewater remediation activities. Our analyses further revealed higher abundances for nutrient removing microorganisms in the Amazon and Galapagos consortia compared with the Highland consortium. Finally, this study also uncovered the contribution of novel microbial groups that enhance wastewater bioremediation processes. These groups have not previously been reported as part of the core microbial groups commonly found in wastewater communities, thereby highlighting the potential of investigating microbial consortia isolated from ecosystems of megadiverse countries like Ecuador.